Conduit cleaning process

Abstract

The in-situ cleaning of conduits is enhanced by the passage therethrough of a propelling gas stream having entrained therein cleaning particles of a regular, non-random configuration, and having less than spherical symmetry.

We claim: 
     
       1. An improved process for descaling and cleaning, in-situ, the interior surfaces of heat exchanger tubes having straight wall sections and a bend, or equivalent helical tube configurations, comprising: (a) introducing cleaning particles having cylindrical configurations in which the diameter is greater than the length of said particles, or equivalent particle shapes, entrained in a propelling gas stream into said heat exchanger tubes to be descaled and cleaned at a gas flow rate corresponding to an outlet gas velocity of from about 5,000 feet per minute up to the sonic velocity of the propelling gas, said particles being of a regular, non-random configuration and having less than spherical symmetry, the cleaning particles impacting the bend and the straight sections at relatively sharp angles of impact for effective cleaning action, said particles assuming an aerodynamic orientation in the gas stream such as to result in a tumbling action upon impact with said bend and straight wall sections that minimizes abrasion of such bends; and   (b) maintaining the flow of said particle-entrained gas stream to the heat exchanger tubes for a time sufficient to effect cleaning in said tubes, whereby the impacts of the cleaning particles with the interior surfaces of the heat exchanger tubes to be descaled and cleaned, and the angle of impact of said particles with said interior surfaces, are such, due to said aerodynamic orientation of the particles in said gas stream, as to maximize desired descaling and cleaning action while minimizing undesired abrasive action so as to enhance the overall heat exchanger tube descaling and cleaning operation.   
     
     
       2. The process of claim 1 and including continuing the flow of the propelling gas to the tubes without said particles therein, at intervals during the overall cleaning operation, so as to remove loose debris from the tubes, and thereafter repeating steps (a) and (b) to further clean the interior walls of said tubes. 
     
     
       3. The process of claim 1 in which said cleaning particles as initially employed have sharp edges at the periphery of the opposite ends thereof. 
     
     
       4. The process of claim 1 in which the opposite ends of the cleaning particles are rounded. 
     
     
       5. The process of claim 1 in which said cylindrical cleaning particles have annular openings extending therethrough. 
     
     
       6. The process of claim 1 in which the outlet gas velocity is from about 7,000 to about 40,000 feet per minute. 
     
     
       7. The process of claim 1 in which the concentration of particles introduced into the tubes is from about 0.1 to about 10 pounds of particles per pound of propelling gas. 
     
     
       8. The process of claim 1 in which the cleaning particles comprise washers. 
     
     
       9. The process of claim 1 in which said cleaning particles have a square configuration. 
     
     
       10. The process of claim 1 in which said particles have a rectangular configuration. 
     
     
       11. The process of claim 1 in which said particles have a triangular configuration. 
     
     
       12. The process of claim 1 in which said particles have a hexagonal configuration. 
     
     
       13. The process of claim 1 in which said particles have a elliptical configuration. 
     
     
       14. The process of claim 1 in which said particles have the configurafion of a boomerang. 
     
     
       15. An improved process for decoking and cleaning, in-situ, the interior surfaces of fired heater tubes used in hydrocarbon or chemical processing, said tubes having straight wall sections and bends, or equivalent helical tube configurations, comprising: (a) introducing cleaning particles having cylindrical configurations in which the diameter is greater than the length of said particles, or equivalent particle shapes, entrained in a propelling gas stream into said fired heater tubes to be decoked and cleaned at a gas flow rate corresponding to an outlet gas velocity of from about 5,000 feet per minute up to the sonic velocity of the propelling gas, said particles being of a regular, non-random configuration and having less than spherical symmetry, the cleaning particles impacting the bends and the straight wall sections at relatively sharp angles of impact for effective cleaning action, said particles assuming an aerodynamic orientation in the gas stream such as to result in a tumbling action upon impact with said bends and straight wall sections that minimizes abrasion of said bends; and   (b) maintaining the flow of said particle-entrained gas stream to said fired heater tubes for a time sufficient to effect decoking and cleaning in said tubes, whereby the impacts of the cleaning particles with the interior surfaces of the fired heater tubes to be decoked and cleaned, and the angle of impact of said particles with said interior surfaces, are such, due to said aerodynamic orientation of the particles in the gas stream, as to maximize the desired decoking and cleaning action while minimizing undesired abrasive action so as to enhance the overall fired heater tube decoking and cleaning operation.     
     
     
       16. An improved process for decoking and cleaning, in-situ, the interior surfaces of fired heater tubes used in hydrocarbon or chemical processing, said tubes having straight wall sections and bends, or equivalent helical tube configurations, comprising: (a) introducing cleaning particles having cylindrical configurations in which the diameter is less than the length thereof, or equivalent particle shapes, entrained in a propelling gas stream into said fired heater tubes to be decoked and cleaned at a gas flow rate corresponding to an outlet gas velocity of from about 5,000 feet per minute up to the sonic velocity of the propelling gas, said particles being of a regular, non-random configuration and having less than spherical symmetry, the cleaning particles impacting the bends and the straight sections at relatively sharp angles of impact for effective cleaning action, said particles assuming an aerodynamic orientation in the gas stream such as to result in a tumbling action upon impact with said bends and straight wall sections that enhances the cleaning action of the particles with respect to said straight sections to be decoked and cleaned; and   (b) maintaining the flow of said particle-entrained gas stream to the fired heater tubes for a time sufficient to effect decoking and cleaning in said tubes, whereby the impacts of the cleaning particles with the interior surfaces of the fired heater tubes to be decoked and cleaned, and the angle of impact of said particles with said interior surfaces, are such, due to said aerodynamic orientation of the particles in the gas stream, as to maximize desired decoking and cleaning action while minimizing undesired abrasive action so as to enhance the overall fired heater tube decoking and cleaning operation.   
     
     
       17. The process of claim 15 in which the outlet gas velocity is from about 7,000 to about 40,000 feet per minute. 
     
     
       18. The process of claim 16 in which the outlet gas velocity is from about 7,000 to about 40,000 feet per minute. 
     
     
       19. The process of claim 15 in which the concentration of particles introduced into the fired heater tubes is from about 0.1 to about 10 pounds of particles per pound of propelling gas. 
     
     
       20. The process of claim 16 in which the concentration of particles introduced into the fired heater tubes is from about 0.1 to about 10 pounds of particles per pound of propelling gas. 
     
     
       21. The process of claim 15 in which said cleaning particles comprise washers. 
     
     
       22. The process of claim 15 in which said particles have a square configuration. 
     
     
       23. The process of claim 15 in which said particles have a rectangular configuration. 
     
     
       24. The process of claim 15 in which said particles have a triangular configuration. 
     
     
       25. The process of claim 16 in which said particles have a square configuration. 
     
     
       26. The process of claim 16 in which said particles have a rectangular configuration. 
     
     
       27. The process of claim 16 in which said particles have a triangular configuration. 
     
     
       28. The process of claim 16 in which said cleaning particles comprise cut wire. 
     
     
       29. The process of claim 15 in which said cleaning particles as initially employed have sharp edges at the periphery of the opposite ends thereof. 
     
     
       30. The process of claim 15 in which the opposite ends of the cleaning particles are rounded. 
     
     
       31. The process of claim 16 in which said cleaning particles as initially employed have sharp edges at the periphery of the opposite ends thereof. 
     
     
       32. The process of claim 16 in which the opposite ends of the cleaning particles are rounded. 
     
     
       33. An improved process for descaling and cleaning, in situ, the interior surfaces of heat exchanger tubes having straight sections and a bend, or equivalent helical tube configurations, comprising: (a) introducing cleaning particles having cylindrical configurations in which the diameter is less than the length of said particles, or equivalent particle shapes, entrained in a propelling gas stream into said heat exchanger tubes to be descaled and cleaned at a gas flow rate corresponding to an outlet gas velocity of from about 5,000 feet per minute up to the sonic velocity of the propelling gas, said particles being of a regular, non-random configuration and having less than spherical symmetry, the cleaning particles impacting the bend and the straight sections at relatively sharp angles of impact for effective cleaning action, said particles assuming an aerodynamic orientation in the gas stream such as to result in a tumbling action upon impact with said bend and straight wall sections that enhances the cleaning action of the particles with respect to said straight sections to be descaled and cleaned; and   (b) maintaining the flow of said particle-entrained gas stream to the heat exchanger tubes for a time sufficient to effect descaling and cleaning, whereby the impacts of the cleaning particles with the interior surfaces of the heat exchanger tubes to be descaled and cleaned, and the angle of impact of said particles with said interior surfaces, are such, due to said aerodynamic orientation of the particles in the gas stream, as to maximize desired descaling and cleaning action while minimizing undesired abrasive action so as to enhance the overall heat exchanger tube descaling and cleaning operation.     
     
     
       34. The process of claim 33 in which said cleaning particles as initially employed have sharp edges at the periphery of the opposite ends thereof. 
     
     
       35. The process of claim 33 in which the opposite ends of the cleaning particles are rounded. 
     
     
       36. The process of claim 33 in which said cleaning particles comprise cut wire. 
     
     
       37. The process of claim 33 in which said cleaning particles have a square configuration. 
     
     
       38. The process of claim 33 in which said particles have the configuration of a boomerang. 
     
     
       39. The process of claim 33 in which said outlet gas velocity is from about 7,000 to about 40,000 feet per minute.